The invention relates to a color filter (CF), and more particularly to a structure of color elements for a color filter. Specifically, the invention is an improvement on a delta-type RGB arrangement to reduce an overlapping area between three adjacent R, G and B elements and reduce an opening area within a non-overlapping portion of three adjacent R, G and B elements, thus promoting color properties, increasing contrast ratio, decreasing light leakage and preventing color mixing.
As scientific technologies and information advance, color filters (CF) have been popularly used in video products, such as color liquid crystal displays, and charge coupled devices and scanners, to obtain color information. With regard to a liquid crystal display (LCD) with light, thin, power-saving and full color features, including super-twisted-nematic (STN) type, thin-film-transistor (TFT) type and metal-insulator-metal (MIM) type, a color filter with three primary colors including red (R), green (G) and blue (B) elements is needed to divide a pixel into R, G and B subpixels. The three primary colors are blended proportionally to create various colors, thus enabling the LCD to display bright, realistic and vivid pictures, enhancing LCD functionality.
The LCD mainly comprises a TFT array substrate, a color filter, and a liquid crystal layer. In a conventional CF process, thin-film color layers including R, G and B layers are successively coated on a glass substrate to serve as R, G, and B elements, after which these must be precisely aligned to pixel areas on the TFT array substrate. In view of manufacturing costs and quality requirements, dyeing, pigment dispersion, printing and electroplating are commonly used to form the R, G and B elements of the color filter. Particularly, pigment dispersion that provides the color filter with high precision and superior light- and heat-resistance has become a major CF process. FIGS. 1A through 1C are top views of stripe, mosaic, and delta RGB arrangement types. The delta-type RGB arrangement provides simplified driving and optimum blend-mode effects, and is thus popularly applied to audio/video products. In addition, a black matrix (BM) is disposed between the R, G, and B elements, shielding TFTs on the TFT array substrate from stray light, and preventing light leakage between pixels.
Recently, the BM pattern has been omitted from the CF substrate to reduce process costs, and the light-blocking area has been replaced by an overlapping portion of adjacent color elements on the CF substrate. FIG. 2A is a top view of a conventional delta-type RGB arrangement with an overlapping portion of adjacent color elements, and FIG. 2B is a cross-section of an overlapping portion of three adjacent color elements shown in FIG. 2A. A conventional color filter 10 comprises a plurality color elements of R, G, and B in a delta-type RGB arrangement. An overlapping portion is additionally formed by adjacent color elements to serve as a light-blocking area. Since each color element has a rectangular profile, however, an overlapping portion 12 is created by three adjacent color elements R, G and B. In FIG. 2B, the overlapping portion 12 is a stack of three color coatings, causing non-uniform distribution in pigment (or dye) thickness on a glass substrate. This protrusion damages uniformity of strength of electric fields and rotation of liquid crystal molecules within pixels, resulting in light leakage, decreased contrast ratio, poor color purity and mixed color.